Comes from tabletop games and other games that use dice in combat mechanics. Generally, when a big fight is about to go down, players will "roll for initiative" and whoever gets the higher roll gets to go first.

So, "roll for initiative" can be used as an (intentionally nerdy) synonym for "initiate a fight".

v. collectively or individually finding someone/something to blame for a problem, as opposed to brainstorming which connotes finding solutions to a problem

n. the act of finding someone/something to blame for a problem

(from a TV ad for HD television)